1. Field of the Invention
The invention relates in general to high speed communication, and in particular, to an amplifier and the method thereof in high speed communication.
2. Description of the Related Art
The demand for high speed communication systems remains high in the recent years. The amplifier in a high speed communication system needs to meet stringent requiems such as broadband input matching, high gain, wide bandwidth, and low noise figure (NF). In addition, it is highly desirable to implement the amplifier in CMOS technology in order to perform a high level of integration, poising design challenges arising from the inferior RF characteristics of CMOS, including large parasitic capacitance, low transconductance, and low supply voltage.
In low noise amplifier (LNA) applications, the most critical parameters are noise figure NF and linearity. Noise figure NF is defined as 10 Log(SNRin/SNRout), with SNRin and SNRout being the input and output signal to noise ratio. Low noise amplifier typically includes a matching network immediately after an antenna to improve noise figure NF. The linearity may be defined by Third Order Input Intercept Point, representing the point at which the power in the third-order product and the fundamental tone intersect.
Two common impedance matching techniques, namely, common gate and resistive shunt feedback circuit configuration are typically used to construct the input impedance matching in LNA, providing wideband impedance matching. Both suffer from channel thermal noise of the transistor, accounted for the dominant noise source in an LNA.
Thus a need exists for an amplifier amplifying an input signal without introducing noise to the amplified signal.